To enter the US you may be required to apply for a VISA. Information can be found at the following links:
 
** http://travel.state.gov/content/visas/english.html
** http://travel.state.gov/content/visas/english/general/visa-wizard.html.
 
A tourism VISA is typically required to attend an educational conference such as IEEE SmartGridComm. Should you need an invitation letter you must be registered to the conference. Then,
 

• Authors of accepted papers can download the letter from EDAS.
• Non-Authors (Speakers, Committee Members and registered attendees) can require a visa letter at the following address: http://visa.comsoc.org.